Build HistoryStore — opt-in git and mode detection

The pro-m1 foundation card. SwiftGitX 0.4.0 (bundled libgit2, the
pathfinder's pin) joins the one target; new Kanban/Git/ holds
BoardGitMode (pure nearest-.git-wins detection, .git-as-file counts,
NSString ancestor walk), HistoryStore (@MainActor @Observable;
compose() is the tier gate — free tier gets no object, no detection,
no stat), GitRepository (scope-confined SwiftGitX handles: create =
init + HEAD forced to main + whole-tree "Initial board state" commit;
branch reads incl. unborn/detached; path-history ranks), GitIdentity
(derived default as a pure function + repo-local config reader — not
libgit2's merged ladder), and GitPathHistory (Mutex-guarded lazy
ranker). beginSession composes the git state beside the tier and
feeds BoardStore.makeIdentityHistoryRanker; git-mode loads pass the
git-backed IdentityHistoryRanker to BoardLoader. The popover's git
slot resolves a pure five-way matrix: free tier unchanged (absent /
BoardGitNote), Pro mode-aware — Add Git on mode none, honest prose on
repo-nested, read-only branch line on git. Provider binding
unchanged: both tiers still bind native until the undo/redo card.

42 new tests across 8 suites, all repositories built through bundled
libgit2; InertGitTests untouched and green. 2194 tests / 375 suites.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

project.yml

@@ -22,6 +22,19 @@ packages:
   IndieAbout:
     url: https://git.rzen.dev/rzen/indie-about.git
     minorVersion: 0.2.2
+  # **The bundled git client** (06-history-undo.md ▸ Rules: "Bundled libgit2 — no git install
+  # required"): SwiftGitX vendors libgit2 as an in-process library, so every git operation the app
+  # performs runs inside the sandbox with no `Process`, no `/usr/bin/git`, and no sandbox extension.
+  # A board's history therefore works identically in a Release build on a machine that has never had
+  # Xcode or the command-line tools installed.
+  #
+  # `exactVersion` rather than a range, and pinned to the pathfinder's own 0.4.0: the package is
+  # pre-1.0 with an API that moves between minors (the commit and diff surfaces this depends on both
+  # changed shape in 0.3→0.4), so a floating pin would be a resolver deciding when the git provider
+  # stops compiling.
+  SwiftGitX:
+    url: https://github.com/ibrahimcetin/SwiftGitX
+    exactVersion: 0.4.0
 
 settings:
   base:
@@ -40,8 +53,11 @@ settings:
 # resources. There is one product, one Info.plist, one entitlements file, one Swift module, and one
 # `.kanban` UTI **exported** (never imported) by the app that owns it.
 #
-# libgit2 arrives here with pro-m1 — a dependency of the one target, dormant behind the subscription
-# gate rather than the contents of a second download.
+# libgit2 arrived here with pro-m1, as SwiftGitX above — a dependency of the one target, dormant
+# behind the subscription gate rather than the contents of a second download. It links into the free
+# app and never runs there: detection itself is tier-gated (`HistoryStore.compose`), so a free-tier
+# session opens without so much as a `fileExists` under `.git` (12-editions.md ▸ The free tier and
+# `.git`, and `InertGitTests`).
 targets:
   # MARK: - Lanework
 
@@ -83,6 +99,7 @@ targets:
       - package: swift-markdown
         product: Markdown
       - package: IndieAbout
+      - package: SwiftGitX
     postBuildScripts:
       - script: '"${SRCROOT}/../indie-skills/skills/app-versioning/scripts/update_build_info.sh"'
         name: Update Build Info